Field of the Invention
The present invention relates generally to a method of mitigating stratification of temperature within the interior of a mobile heated cabinet. It also relates to such a mobile heated cabinet that mitigates stratification of temperatures.
Description of the Related Art
Heated cabinets for heating, holding, and/or proofing food are commonly used in the food service industry, for example in hotels, school cafeterias, restaurants, bakeries, and the like. These heated cabinets can control the temperature within the cabinet, and may be used to cook food, and to keep prepared food at certain temperatures. In many of these applications food may be placed in the cabinet at a stationary location such as a kitchen, and the loaded cabinet may then be transported over large distances during which it may not be connected to an external power source.
Electric heating elements are provided in heated cabinets to warm food stored therein. As seen in U.S. Pat. Nos. 4,776,317 and 5,276,309, fans can be installed near an electric heating element. The fans are provided to force air to move over the electric heating element in order to heat the air and guide the heated air into a food storage area of the heated cabinet. However, such fans often do not uniformly distribute the heated air throughout the heated cabinets and changes in distribution of the generated heat can occur when the cabinet is moved from a stationary location where it is connected to an external source of electrical power. Thus, stratification of temperatures of the interior of the heated cabinets can occur.
Normally, heated cabinets must be plugged into a power source to provide energy to both fans and electric heating elements. When a heated cabinet is to be moved from one location to another, however, the power supply is disconnected and heating from the electric heating elements and air circulation from the fan are discontinued. Because of large power requirements of electric heating elements and certain other electrical components of heated cabinets, it has been thought to be impractical to provide power to such cabinets during transportation from an alternative power source. As a result, heat loss and temperature stratification occurs, which may result in food safety issues as well as quality and consistency issues.
One device known in the art is described in JP 10-234590, which is directed to a mobile warming device that generates heat from two separate heating sources in order to provide heat to a food storage area of a heated cabinet during transportation from one location to another. The first source is an electric heating source that is disposed inside the food storage area of the mobile cabinet. The second heating source is a heat accumulator having an insulation layer that surrounds another electric heating source embedded in a thermal storage medium. In between the insulation layer and the embedded electric heating source is a channel that allows for the flow of air. The heat accumulator uses a fan to guide air around the embedded electric heating source, thus, heating the air. The fan can then blow the heated air into the food storage area.
As disclosed in JP 10-234590, when the mobile warming device is connected to an external power supply, the first heating source heats the food inside the food storage area to about 80° C., and the embedded electric heating source heats the thermal storage medium to temperatures of about 300 to 400° C. When external power is unavailable, both the first heating source and the embedded electric heating source are turned off. In order to provide heat, a rechargeable battery is connected to a controller and the fan of the heat accumulator. When external power is unavailable, the fan is turned on to move previously heated air, which is guided from the thermal storage medium.
Other prior art devices are known but these are not understood to power a fan associated with the interior of a heated cabinet when it is disconnected from an external power source.
In heated cabinets such as discussed above, fans are provided to force heated air into the food storage areas of heated cabinets. However, such heated cabinets may not prevent temperature stratification within the food storage area when the cabinets are connected to an external power supply. Temperature stratification can also occur when the power supply is disconnected because the fan is provided near a heating source and only heated air is forced into a food storage area. In such heated cabinets, fans are not provided to circulate air within the food storage area in order to provide a uniform temperature throughout the food storage area whether an external power supply is available or not.